The basic design of the bicycle has remained unchanged for several decades. Even racing bicycles, in spite of weight reductions and significant improvements in equipment, remain derivative of the old "sit-up and beg" machines used for anything from shopping to cross country cycling. These bicycles typically include the classic diamond frame with front and rear wheels, the rear wheel being driven by a pedal crank located intermediate the front and rear wheels and a chain drive connected to a rear axle mechanism, generally having a multispeed derailleur device located at the rear wheel for changing speeds. A major cause of both friction losses and distortion in the traditional frame lies in the use of such a remote chain wheel and sprocket system transmitting power from the bottom bracket of the frame to the rear wheel. Further, with such a traditional design the center of effort (the pedal crank axis) located ahead of the rear wheel, results in both the imposition of torsional stresses on the frame and in the fact that on the downward stroke the force which the rider can apply is limited to a little more than his or her weight unless a much greater and less easily sustainable effort is applied through the handlebars and the rider's body. Another fact of the traditional bicycle is that the rider presents a large frontal area to the air, causing a significant effort to be expended in overcoming wind resistance. Even in the racing "crouch" position, this effort is considerable.
It is to these basic concepts of the traditional bicycle that the present invention is directed. In the present invention, each of the above stated problems have been solved in a novel and elegant manner to provide an efficient and practical human-powered vehicle capable of achieving relatively high speeds in a far more efficient manner with less cyclist fatigue than heretofore known.
Further, improvements in materials technology and increased understanding of the hydrodynamic behavior of fluids has, in recent years, led to increased interest and application of traction (or gearless) drive systems. Such systems offer high efficiency, smooth power transmission, quietness and enhanced reliability together with the almost unique characteristic of permitting continuous variation in the speed ratio.